Tonneau cover



FIG. 1 is a top perspective view of a tonneau cover showing the new design;

FIG. 2 is a right side elevational view thereof, the left side elevational view being a mirror image;

FIG. 3 is a rear elevational view thereof, the front elevational view being a mirror image; and,

FIG. 4 is a top plan view thereof.

In the drawings, the broken lines depict a truck only and form no part of the claimed design. 

The ornamental design for a tonneau cover, as shown and described. 